Interlocking device



Dec. 15 1925- E. K. READ INTERLOCKING DEVICE Filed Sept- 24, 1920 WITNESSES: Q ff f zjfiw m/ W I mvsmon EfiQtStKBtdd av ATTORNEY Patented Dec. 15, 1925.

UNITED STATES P TEN -onion.

nnNEs'r'K. READ, 0F WILKQINSBURG, PENNSYLVANIA, 'ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF- PENNSYLVANIA.

INTERLocmNd- DEVICE.

Application filed September 24, 1920. Serial No. 412,544.

T 0 all whom it may concern."

Be it known that I, ERNEST K. READ, a

citizen of the United States, and a resident of VVilkinsburg, in the county of Allegheny and State of Pennsylvania, have invented a,

new and useful Improvement in Interlocking Devices, of which the following is a specification.

My inventionrelates to mechanical interlocking devices adapted to insure proper sequence in the operation of a plurality of controlling levers, such as are used to operate electric-switch apparatus.

The invention is designed especially for use in connection with electric motors that require a relatively low voltage when being started. and a much higher voltage to bring themup to, and to maintain, normal running speed. 1

My invention has, for its object, the provision of means whereby the switch which controls the low-voltage circuit must be moved to starting position before the switch controlling the high-voltage circuit can beclosed;

whereby the high-voltage circuit must be.

closed immediately after the low-voltage switch has been closed and whereby each switch is held against, closing movement.

while the other switch is in closed position.

In the operation of large motors, which must be started under low voltage, a switch is usually provided to control the lowvoltage .circuit utilized in starting, and another switch, known as the. running switch, is provided to control a high-voltage circuit. If the switches are not closed in'the proper sequence or are both in closed position at the same time, serious injury to the operator and to the electrical apparatus is likely to result. Various types of apparatus have been adopted to prevent such. accidents, but, in

many of them, it is possible to start the position.

Figure '1 of the drawing is a plan view of a pair of switch levers with my invention applied. thereto;

Fig. 2 is a side elevation thereof, and I Fig. 3 is a view taken along the line of IIIIII of Fig. 2.

My device is illustrated as. applied to a lever 4 for operating a starting switch (not shown) and to a lever 5 for. operating a runnlng switch (not shown). These levers are pivoted to a supporting structure, as indicated at 6 and 7 in the usual manner. Im

Inediately above the levers, I provide a plvotal support 8 on which are loosely mounted arms 9. and 10, the arm 10 being weighted at the end which projects past the lever 4, as shown in Figs. 1 and 3..

Referring more particularly to Fig; 3,

.the running-switch lever 5, when moved to its upper position, closes the running switch, and, when movedto the position indicated in dotted lines, opens the switch; while the lever 4 in its lower; position, maintains the starting switch in open position and, when advanced to the position indicated in dotted lines, closes the'starting switch. It will be seen that the arm 9 extends across these .leversand prevents them from simultane ously occupying their uppermost, or closed positions.

The arm 10 is weighted at the end which extends across the lever d and has its other end normally lying in approximately the horizontal plane occupied by the running-;

switch lever 5, when in retracted or open As shown in Fig. 3, the running switch 5 is ,in closed position and the starting switch 4- is in open position, and switch lever 4 cannot be advanced to closed position until the lever 5 is retracted, and,

when lever 4 is in advanced position, the lever 5 cannot be advanced until lever 4 is returned to neutral position.

Starting with levers 4 and 5, both in retracted positions, the running-switch lever 5 cannot be advanced because of the fact that the lower end of the weighted lever 10 engages the side of thelever, and the jamming action therebetween prevents upwardmovement of the lever. However, if the lever 4. be advanced to the position in dicated in 'dotted lines it will disengage the arm 10 from the lever 5, and, upon being retracted, the lever 5 may be advanced quickly, before the arm 10, through the action of gravity, again engages it. The purpose of limiting the time within which the lever 5 may. be advanced is to provide against a workman, after he closes the start ing-switch lever i and returns it to open position, from waiting too long before closing the running-switch lever. If too long a time elapses after the operation of the starting-switch lever, the motor will have lost its starting momentum, and the running-switch lever cannot, of course, be safey advanced to closed position.

It will be clear, therefore, that, with the arm 9 preventing both levers being in advanced position at the same tinfie, and the arm l0 permitting advancement of the lever 5 only within a very limited time after retraction of the lever 4-, I provide a means whereby the operation of thelevers in their proper sequence is ensured, and means whereby the running lever niay be advanced only within a limited period after the motor has been started.

Various changes may be made in the de vice within the scope of the invention, as defined within theclaims.

I claim as my invention l 1. In an interlock device, the combination with a pair of levers, of an arm pivoted intermediate its ends and having each end extending across one of the levers to prevent either of said levers being moved to advanced position while the other lever is in advanced position, a second arm pivoted intermediate its ends and having a Weighted end extending across one of the levers and the other end extending downwardly in position to normally abut the side of the other lever to maintain it normally in retracted position.

2. In combination, in an interlock device, a starting-switch lever and a running-switch lever, an arm pivoted intermediate its ends and extending across the levers to prevent either lever occupying an advanced position while the other lever is advanced, and

a pivoted arm having one end normally in locking engagement with the runningswitch lever and having lllS, other end weighted and extending across, the startingswitch lever in position to be moved by such lever when in advanced position and to thereby free the running-switch lever from engagement with the other end of said arm.

3. In combination, in an interlock mechanism, a pair of levers, means for preventing both of said levers from simultaneously occupying advanced positions, and a gravity-operated member normally engaging one of said levers to prevent advancement thereor until after the other lever has been operated to disengage the gravity-operated member.

4. In combination, in an interlock mechanism, a pair of levers, means for prevent ing both of said levers from simultaneously occupying advanced positions, an arm normally engaging one of said levers to prevent advancement thereof until after the other lever has been advanced to disengage said arm and returned to retracted position, and means for limiting the period of time following the retraction of the said other lever during which the arm is so disengaged;

5. The combination with two switch members, ofa plurality of arms, one of which comprises a gravity-controlled element, for preventing an operation of onemeinber af ter a predetermined interval subsequent to the operation or". the other one of said members.

6. The combination with two switch operating levels, of means for controlling the sequence of their movements and a gravity-controlled device for determining the period within which one of said movements may take place. 7

In testimony whereof, I have hereunto, subscribed my name this 17th day of September 1920.

ERNEST K; READ. 

